METHOD AND APPARATUS FOR PRODUCING CROSS-WOUND BOBBINS

Abstract

In a process for producing cross-wound packages in a yarn winding device of a textile machine, the helix angle of the wound-on yarn changes during winding on. The helix angle is a variable chosen in dependence on the diameter of the yarn package. This diameter of the package is in turn calculated on the basis of the length of the yarn already wound on. An arrangement for producing cross-wound packages on a number of yarn winding devices comprises a drive for rotating the cross-wound package. A variable, driveable yarn guide is provided at each yarn winding device for laying a yarn in axial direction of the cross-wound package at a variable helix angle. A common sensor for measuring the package diameter at a number of yarn winding devices is provided, which sensor can be positioned to the yarn winding devices one after another.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a process and an arrangement for producing cross-wound packages at a yarn winding device of a textile machine, in which the helix angle of the wound-on yarn changes during the winding on process. The arrangement comprises a drive for rotating the cross-wound package and also comprises on each yarn winding device a variably driveable yarn guide for laying a yarn to be wound in axial direction of the cross-wound package at a variable helix angle.

In place of the helix angle, the so-called cross-over angle is often also used. The value of the cross-over angle approximates to double the value of the helix angle.

A process and an arrangement of the above mentioned type is prior art in German published patent application DE 10342 66 A1. The aim of the invention disclosed in DE 10342266 A1 is the production of a cross-wound package having a hard core and a high density in the inner area and a lower in the outer area. The yarn is wound on at the beginning of the package build-up at a small helix angle and the helix angle is either continuously increased or increased at short intervals. No details are disclosed regarding how the amount of the increase is selected, nor whether the increases are variable or not, and if so, how. The cross-wound package produced according to the process in German published patent application DE 10342266 A1 has random winding, as the so-called winding ratio constantly changes during the winding process. The winding ratio is defined as the number or revolutions of the cross-wound package during a double lift of the yarn guide over the width of the cross-wound package. There is therefore always the risk that the winding ratio takes on integral values and so-called ribbon winding zones arise, which have an extremely negative influence on the unwinding behaviour of the cross-wound package. An additional device must accordingly be on hand to prevent the occurrence of ribbon winding zones. There are no details provided in the prior art document.

It is an object of the present invention to improve a process and an arrangement for producing cross-wound packages.

The object of the present invention has been achieved in that the helix angle is selected based on the package diameter, and that the package diameter is calculated based on the length of the yarn already wound on. In the case of the arrangement, the object has been achieved in that a control system is provided for calculating the cross-wound package diameter from the length of the yarn already wound on, said control system being connected to the drive of the yarn guide.

The invention has the advantage that the cross-wound package diameter is known at any given time. In the known arrangement this could only be achieved up to now in that a sensor was placed at each winding head, which sensor measured the cross-wound package diameter. The present invention omits this diameter-measuring sensor at each winding head.

As the cross-wound package diameter is known at any given time, the rotational speed of the package and therefore also the actual winding ratio at any given time can be calculated with the aid of the also known rotational speed of the cross-wound package. The cross-wound package is driven on its periphery via a winding roller and rotates as a result at a circumferential speed which essentially corresponds to the speed of the winding roller. The yarn guide for placing the yarn to be wound in axial direction of the cross-wound package is provided with a speed-regulating drive, which is regulated by the control system, so that the speed of the yarn guide is also known. As a result the winding ratio is computable in the control system so that the winding ratio is known at any given time during the production of a cross-wound package.

The known cross-wound package diameter permits the controlled winding-on of the yarn constantly at the most optimal helix angle. Cross-wound packages can be produced which can be adapted to subsequent processing stages. Good unwinding properties of the cross-wound package can be achieved for example with a relatively large helix angle at a small cross-wound package diameter, and helix angles decreasing with the cross-wound package diameter. Cross-wound packages with a high density, which are particularly suitable for further processing in weaving mills, or dye packages having a particularly homogenous package form, can be produced selectively.

In the production of cross-wound packages with random winding, the winding on of the yarn with undesirable winding ratios which lead to ribbon winding zones, can be effectively prevented, as the winding ratios can be adapted shortly before the occurrence of a non-desirable value by means of a variation of the helix angle by changing the yarn guiding speed.

It is in addition possible to produce cross-wound packages with step-by-step precision winding, in which the winding ratio is kept constant over a range of diameter areas.

The present invention is particularly suitable for spinning machines, in which the yarn is delivered at a known delivery speed which is usually constant. The length of the wound-on yarn is determinable by the control system directly from the known delivery speed. In order that the yarn is wound on at a constant tension at a constant delivery speed, it is necessary that in the case of a change in traverse speed of the yarn guide in order to change the helix angle, the circumferential speed of the winding roller simultaneously changes inversely to the change in speed of the yarn guide, so that the resulting winding-on speed remains constant. As the cross-wound package diameter is known from the control system, it can be provided that the yarn tension is optimized in certain diameter areas of the cross-wound package. For example it can be advantageous to wind the yarn on at a somewhat higher level of tension in the lower diameter area in order to improve the stability of the cross-wound package.

The present invention can also be applied just as well to winding machines. The length of the yarn already wound on can be calculated at the winding machine from the winding-on speed, which results from the addition of the vectors of the circumferential speed and the traverse speed. The yarn tension can be regulated at the winding machine by means of a yarn brake, so that in the case of a change in the traverse speed for changing the helix angle, a simultaneous adaptation of the circumferential speed of the winding roller is not absolutely necessary.

In order to increase the exactness in specifying the length of the wound-on yarn it can be advantageous to gauge the speed of the wound-on yarn directly. The yarn speed can for example be detected by a non-contact speed sensor arranged upstream of the winding head.

The calculation of the cross-wound package diameter with the aid of the length of the yarn already wound-on can take place in that a mathematical model is stored in the control system of the textile machine or in the winding head's own control system, said mathematical model having been ascertained from preliminary tests. The mathematical model can be stored for a given yarn having specified yarn parameters, such as material, twist and fineness, with known cross-over angles and known yarn tension, whereby based on the diameter of the tube the cross-wound package diameter can be constantly measured and stored as a function of the length of the wound-on yarn. With the aid of this mathematical model stored in the control system, the cross-wound package diameter can be calculated with the aid of the length of the yarn already wound on at every winding head of the textile machine, without any further evaluations of the diameter being necessary. It can be advantageous that in the calculation of the cross-wound package diameter, the yarn tension and/or the cross-over angle, at which the yarn is wound on, is taken into consideration. The exactness of the mathematical model can be increased when the yarn tension and the cross-over angle can also be taken into consideration as variables.

In a further embodiment of the present invention it can be advantageous that at specified intervals a reference evaluation of the cross-wound package diameter is carried out, in order to correct the calculated value of the cross-wound package diameter. The variables used for the calculation of the cross-wound package diameter, such as the length of the wound-on yarn, are subject to tolerances, so that the calculated cross-wound package diameter can deviate from the actual value. These inaccuracies can be adjusted by means of a reference evaluation of the cross-wound package diameter. The collected data on the actual value of the cross-wound package diameter can be used as a new base for further calculations of the cross-wound package diameter, so that incorrect values arising from tolerances in the measurement of the cross-wound package diameter do not reach an unacceptable level. A reference measurement of the calculated cross-wound package diameter can be carried out by a common sensor for measuring at a number of winding devices. The sensor can be positioned to the winding devices one after the other and is arranged advantageously on a mobile carriage which travels along the textile machine. Only one sensor is necessary for the entire textile machine, so that the configuration of the winding device without its own diameter sensor is still very simple. It can also be advantageous to adapt and optimize the mathematical model for the calculation of the cross-wound package diameter with the aid of the measured values delivered by the sensor. Precision in the formation of the cross-wound package in accordance with the desired properties of the cross-wound package, for example good unwinding properties, can hereby be further improved.

The sensor can measure the diameter of the cross-wound package in various and selectable ways. The sensor, for example, can be positionable directly to a cross-wound package and can scan the diameter of the cross-wound package in a non-contact manner. The measurement of the cross-wound package can also take place indirectly, in that the sensor is positionable to a package cradle for taking-up the tube of the cross-wound package. The cross-wound package diameter can be calculated by mechanical or optical scans of the position of the package cradle above the winding roller.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a very schematically shown side view of a spinning machine in the area of a winding head,

FIG. 2 is a frontal view of the spinning machine of FIG. 1 comprising a number of adjacent winding heads,

FIG. 3 shows velocity vectors.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 depict a very schematic section of a spinning machine. A yarn produced in a spinning unit 1 is withdrawn by means of a delivery roller pair 3, 4 out of the spinning unit 1 and fed at a delivery speed to a winding head 5 and wound onto a cross-wound package 6. The spinning unit 1 can be optional, for example an air jet spinning arrangement or an open-end spinning arrangement. The production of a yarn in such spinning units is known and needs no further explanation. The delivery roller 3 of the delivery roller pair 3, 4 is driveable by means of a drive 7 and transports the yarn nipped between the delivery rollers 3 and 4 at as constant delivery speed v₁ as possible in order to ensure a uniform yarn formation. From the delivery roller pair 3, 4, the yarn 2 reaches the cross-wound package 6 via a stationary yarn guide 8 and a yarn guide 9 traversing in the direction of the double arrows B. The cross-wound package 6 comprises a tube 10 and a cylindrical or conical yarn body 11, which is formed by means of the yarn 2 being wound in layers onto the tube 10. The tube 10 has a hinged support in a package cradle 12 and the cross-wound package 6 lies with its outer peripheral surface on a winding roller 13. The package cradle 12 is swivel-mounted on an axle 14 and, if required, loading devices could be arranged to the package cradle 12 (in a way not shown), said loading devices increasing the pressure of the cross-wound package 6 to the winding roller 13. The winding roller 13 is driven to rotate by a drive 15. The cross-wound package 6 rotates at a circumferential speed v₂ of the winding roller 13. As the cross-wound package diameter D of the cross-wound package increases with the amount of wound on yarn 2, the speed of the cross-wound package 6 changes at the given speed v₂.

The yarn guide 9 traversing in direction B serves to place the yarn 2 to be wound in axial direction of the cross-wound package, while the cross-wound package 6 is driven to rotate by the winding roller 13. The yarn 2 is wound in a helical curve shape at a helical angle α onto the cross-wound package 6. The yarn guide 9 moves at a traversing speed v₃, which when changed also renders the helix angle α changeable. The addition of the vectors of the circumferential speed v₂ and the traversing speed v₃, which are perpendicular to one another, results in the winding speed v₄, at which winding speed v₄ the yarn 2 runs onto the cross-wound package 6.

The yarn guide 9 is depicted in this shown example in the form of a ring applied to a pivot lever 16, which yarn guide 9 can move axially to and from to the cross-wound package in traversing direction B by means of the drive 17 which is connected to the pivot lever 16. The embodiment of the yarn guide 9 and its drive are just simply examples and can just as well have different designs. For example the yarn guide 9 can also be two impeller wheels rotating in opposite directions, which set the yarn in traverse motion.

The drive 17 of the yarn guide 9 and the drive 15 of the winding roller 13 are connected to a control system 18. The control system 18 controls the drives 15 and 17 in such a way that the desired circumferential speed v₂ and the traversing speed v₃ are given. The control system 18 is also connected to the drive 7 of the delivery roller pair 3, 4. When the control system 18 does not control the drive 7, it receives at least information on the delivery speed v₁ of the delivery roller 3, 4.

At a constant delivery speed v₁, it is important that also the winding speed v₄ remains essentially constant. The winding speed v₄ can vary slightly from the delivery sped v₁ in order to ensure a specific yarn tension of the yarn 2. With the aid of the control system 18, the circumferential speed v₂ and the traversing speed v₃ can be so controlled that the helix angle α is changeable while the winding speed v4 remains constant thereby. An example is shown in FIG. 3 in which the helix angle α is to be increased to a larger helix angle α′. For this purpose, the circumferential speed v₂ is reduced to the value v′₂ and the traversing speed v₃ is increased to the value v′₃.

In accordance with the present invention it is provided that the helix angle α is selected based on the cross-wound package diameter D, in order to produce a cross-wound package 6 with specified properties. The cross-wound package diameter D is calculated on the basis of the length of yarn 2 already wound on. For this purpose a mathematical model is stored in the control system 18, with which the cross-wound package diameter D is calculable on the basis of the length of yarn 2 already wound on.

To increase accuracy, a common sensor 19 is provided on a number of winding heads 5 for measuring the cross-wound package diameter D. As can be seen in FIG. 2, a number of spinning units 1 and the respective winding heads 5 are arranged adjacently to one another in the spinning machine. Standard spinning machines comprise several hundred spinning units 1 adjacent to one another, each of which produces a yarn 2 simultaneously. A mobile unit 20 is arranged to the spinning machine and is movable in longitudinal direction of the spinning machine, which mobile unit 20 can be positioned to individual winding heads 5 or to the spinning units 1. The mobile unit 20 can, for example, be a maintenance device, which serves to repair end breaks in the spinning unit 1 and/or to replace a full cross-wound package 6 with an empty tube 10. The sensor 19 is arranged on the maintenance device 20. The sensor 19 measures the diameter D of the cross-wound package 6 at that winding head 5 past which the maintenance device 20 has just moved. The sensor 19 can hereby, for example, as denoted by the broken-lined arrow 21, read the surface of the yarn body 11 directly and thus calculate the cross-wound package diameter D.

Alternatively it can be provided that the sensor 19 determines the cross-wound package diameter D when the maintenance device 20 stops at a spinning unit in order to repair an end break.

It can be advantageous that, for example, the sensor 19 scans the position of the package cradle 12, as denoted by the broken-lined arrow 22. The reading of the position of the package cradle 12 is an indirect measurement for the cross-wound package diameter D. The measuring of the package cradle 12 can, for example, take place either mechanically by means of a lever or also in an optical, non-contact way.

Due to the controlled measurements at specified intervals of the cross-wound package diameter D by the sensor 19, determined values of the cross-wound package diameter D can be corrected in the control system 18. The diameter values collected by the reference measurement at one winding head can be used as the basis for further calculations of the cross-wound package diameter, so that the calculated value is significantly more accurate. It can also be provided that by means of each measured cross-wound package diameter D, the mathematical model stored in the control system 18 can be improved and optimized for the calculation of the cross-wound package diameter D. In so doing, the accuracy of the diameter calculations at all winding heads 5 are improved. With the application of the present invention, cross-wound packages 6 having exactly defined properties can be produced very simply and cost-effectively for further processing, without a sensor 19 for continuous scanning of the cross-wound package diameter D being present at each individual winding head 5.

Claims

1. A process for producing cross-wound packages at a winding head of a textile machine, whereby the helix angle of the wound on yarn changes during winding on, characterized in that the helix angle is selected in dependence on the cross-wound package diameter, and in that the cross-wound package diameter is calculated on the basis of the length of the yarn already wound on.

2. A process according to claim 1, wherein in the calculation of the cross-wound package diameter, the yarn tension and/or the helix angle, with which the yarn was wound on, is taken into consideration.

3. A process according claim 1, wherein a reference measurement of the cross-wound package diameter is carried out, in order to correct the calculated value of the cross-wound package diameter.

4. An arrangement for producing cross-wound packages (6) at a number of winding heads (5) of a textile machine comprising a drive (13) for rotating the cross-wound package (6) and also comprising at each winding head (5) a variably driveable yarn guide (9) for placing a yarn (2) to be wound on in axial direction of the cross-wound package (6) at a variable helix angle (α), wherein a control system (18) for calculating the cross-wound package diameter (D) on the basis of the amount of yarn (2) already wound on is provided, said control system (18) being connected to the drive (17) of the yarn guide (9).

5. An arrangement according to claim 4, wherein a common sensor (19) is provided for measuring the cross-wound package diameter (D) at a number of winding heads (5).

6. An arrangement according to claim 4, wherein the sensor (19) is positionable to the winding heads (5) one after another.

7. An arrangement according to claim 4, wherein the sensor (19) is arranged on a travelling carriage (20) which is driven along the length of the textile machine.

8. An arrangement according to claim 4, wherein the sensor (19) is positionable directly to a cross-wound package.

9. An arrangement according to claim 4, wherein the sensor (19) is positionable to a package cradle (12) for taking up a tube (10) of the cross-wound package (6).